Japan's Omocoro performed an unusual experiment in Shibuya recently which attempted to discover whether it was possible to track Twitter users down in real life just by using their Twitter feeds.

The writer, called Sebuyama, set about tracking down three targets in the Shibuya area and chronicled his investigation.

Shibuya is one of Japan's busiest districts. Its famous crossing, the Shibuya sprawl, is said to have over 45,000 people crossing it every 30 minutes. It is one of the most 'checked in' locations in the world.

It is also densely packed, with hundreds of shops and restaurants, making it a prime location for tracking down some avid Twitter users.

First, Sebuyama filtered results by looking for people tweeting that they were "now in Shibuya." He apparently found around 30 tweets within a minute, and from this list he picked out three victims to hunt down.

Many Japanese Twitter users do not use real pictures of themselves, which helped narrow down his chosen three, but he also looked at physical descriptions used on their Twitter profiles.

Perhaps most frightening, he was able to follow these users from tweets about where they were shopping, pictures of their lunch and comments on purchases. Although he lost the first target because she moved around too much, he was able to track the other two down pretty easily.

Understandably the two Twitter victims were surprised and shocked to have a random stranger find them, identify them by their Twitter user name and even tell them what they had just eaten for lunch.

The experiment serves up an eerie lesson about posting personal information on Twitter, but the column has also spread through Japan's social networks, with many commenting on how "scary" it is.

Sebuyama has achieved his goal with this experiment, proving effectively that we just don't think about the information we're putting online.

He made sure to punctuate the end of his column with photos of himself sitting in a darkened room with his laptop, ominously holding a knife.

The imagery is on the money.

We should be scared at how easy it is to track people down. Not everyone openly shares personal information on Twitter, but even those who don't might also be using Foursquare or Facebook to talk about their daily activities.

It would be interesting to see how well such an experiment would work in other major cities, like London or New York.

I'm not sure whether or not the kind of personal information shared by Japanese users on Twitter is more open than their western counterparts. Either way, I think we'd be surprised by how easy to catch we all are.